BRUSSELS — NATO’s top official says Russia’s military intervention in Ukraine is in violation of the U.N. charter and threatens peace and security in Europe.

NATO General Secretary Anders Fogh Rasmussen spoke Sunday before going into a meeting of the North Atlantic Council, the alliance’s political decision-making body.

“What Russia is doing now in Ukraine violates the principles of the United Nations charter. It threatens peace and security in Europe. Russia must stop its military activities and threats,” he said.

The NATO secretary general said he called the meeting “because of Russia’s military action in Ukraine and because of President (Vladimir) Putin’s threats against this sovereign nation.”

Rasmussen said officials will discuss Russia’s activities in the Crimean Peninsula and “their implications for European peace and security and for NATO’s relationship with Russia.”

Rasmussen tweeted on Saturday that the North Atlantic Council will hold a meeting Sunday about Russia’s invasion of Ukraine.

On Saturday, Russian lawmakers approved Russian President Vladimir Putin’s request to move troops to Ukraine, while the Ukrainian acting president Oleksandr Turchynov put his country’s military on higher alert, according to media reports. Russian troops began occupying the Crimea region of Ukraine on Friday and pro-Russian protests were held Saturday in the Russian-speaking eastern parts of the country.

“The stakes are significant for both the U.S. and Russia, as well as for Europe and NATO,” retired Adm. James Stavridis, former NATO supreme allied commander, said in an email Saturday to Military Times.

“Many will consider any level of NATO involvement provocative and potentially inflammatory,” Stavridis wrote. “Unfortunately, the stakes are high and the Russians are moving. Sitting idle, without at least looking at options, is a mistake for NATO and would itself constitute a signal to Putin — one that he would welcome.”

Speaking from the White House on Friday, President Obama said the U.S. government is “deeply concerned” about reports of Russian military movement inside Ukraine.

“The United States will stand with the international community in affirming that there will be costs for any military intervention in Ukraine,” Obama said.

U.S. Sen. John McCain, R-Ariz., called on Obama to spell out exactly what those costs will be.

“Every moment that the United States and our allies fail to respond sends the signal to President Putin that he can be even more ambitious and aggressive in his military intervention in Ukraine,” McCain said in a statement issued on Saturday “There is a range of serious options at our disposal at this time without the use of military force. I call on President Obama to rally our European and NATO allies to make clear what costs Russia will face for its aggression and to impose those consequences without further delay.”

Staff writer Jeff Schogol and the Associated Press contributed to this report.